A term used to describe an individual that has the ability to dominate another individual or group of individuals in a distasteful and embarrassing manner - mainly used to describe raid or particularly difficult groupable mobs in Everquest.

"Oh man, this guy is an assbeat"

"We got fucked over by that assbeat."

"Our raid was going pretty well until the assbeat woke up.. it was like throwing a young schoolboy in between two Catholic priests and watching them fight to the death."